The National Aeronautics and Space Administration (NASA) is in the business of completing interplanetary missions. NASA headquarters are located at 300 East Street, Southwest, Washington, D.C. NASA's planetary surface exploration missions that have landed on the surface of Mars included one or more sun sensors. The sun sensors have been used to determine the direction of a rover or to establish three-axis attitude information to point a high-gain antenna toward the earth. A Micro-sun sensor (MSS) is being developed and flight qualified for future Mars missions. The MSS is a miniaturized pinhole camera consisting of a mask, a spacer, and a focal plane. The focal plane is an active pixel sensor (APS) chip and the optics is a piece of silicon wafer coated on one side with a 300 nanometer (nm) thick gold layer perforated by an array of pinholes of ˜50 micrometer (μm) diameter. This serves the purpose of a mask, and is mounted on a spacer ˜1000 μm from the APS, making the system a pinhole camera. The sun's rays penetrate the silicon mask through the pinholes and form an image on the APS. On the basis of the location of the image on the APS, the MSS determines sun angles that can be used to compute location coordinates with respect to the sun. However, this setup suffers from multiple internal reflections from the focal plane onto the back of the reflective gold-coated mask, and back onto the focal plane, thereby causing ghost images. The ghost images severely limit the accuracy of the MSS. This problem can be corrected by employing an antireflective surface on the back of the mask.
Many different types of anti-reflection surfaces have been described in the prior art. For example, a porous silicon surface has been used as an antireflection surface. While antireflective, such a structure is easily damaged. As another example, a sub-wavelength structure with a surface grating period smaller than the light wavelength has been used for an antireflection surface; however, creation of the structure requires an expensive fabrication process.
While prior art exits, nothing heretofore devised can be economically created and be strong enough so that it is not easily damaged. Thus, a continuing need exists for an anti-reflection surface that can be economically created and used in a myriad of applications.